New breed of medium voltage converters

Advances in power semiconductor technology have made it possible to produce high-power pulse width modulated, voltage source inverter variable-speed drive systems in the medium-voltage supply range (2.4-11 kV), with power ratings in the range 1-14 MW. This article describes the design, development and prototype testing of a state of the art converter which delivers variable frequency sinusoidal voltage at its output terminals. The main feature of the converter is the use of series 3.3 kV, 1200 A IGBTs and a sine-wave-output filter. The design limitations of PWM IGBT converters, inherent in modern devices, are briefly summarised. These have been overcome by the use of a sine-wave output filter.